US4732706A - Method of preparing low viscosity, electrically conductive ferrofluid composition - Google Patents
Method of preparing low viscosity, electrically conductive ferrofluid composition Download PDFInfo
- Publication number
- US4732706A US4732706A US07/054,412 US5441287A US4732706A US 4732706 A US4732706 A US 4732706A US 5441287 A US5441287 A US 5441287A US 4732706 A US4732706 A US 4732706A
- Authority
- US
- United States
- Prior art keywords
- surfactant
- ferrofluid
- composition
- particles
- ferrofluid composition
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 239000011554 ferrofluid Substances 0.000 title claims abstract description 96
- 239000000203 mixture Substances 0.000 title claims abstract description 89
- 238000000034 method Methods 0.000 title claims description 27
- 239000004094 surface-active agent Substances 0.000 claims abstract description 54
- 239000007788 liquid Substances 0.000 claims abstract description 50
- 230000005291 magnetic effect Effects 0.000 claims abstract description 31
- 239000003093 cationic surfactant Substances 0.000 claims abstract description 30
- 229920005862 polyol Polymers 0.000 claims abstract description 16
- 239000006249 magnetic particle Substances 0.000 claims abstract description 13
- ZUHZGEOKBKGPSW-UHFFFAOYSA-N tetraglyme Chemical compound COCCOCCOCCOCCOC ZUHZGEOKBKGPSW-UHFFFAOYSA-N 0.000 claims abstract description 9
- 239000002245 particle Substances 0.000 claims description 67
- 230000005294 ferromagnetic effect Effects 0.000 claims description 22
- 239000006229 carbon black Substances 0.000 claims description 19
- 239000003795 chemical substances by application Substances 0.000 claims description 18
- -1 alkylene polyol Chemical class 0.000 claims description 17
- 239000003945 anionic surfactant Substances 0.000 claims description 12
- 125000001453 quaternary ammonium group Chemical group 0.000 claims description 11
- 238000010494 dissociation reaction Methods 0.000 claims description 8
- 230000005593 dissociations Effects 0.000 claims description 8
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 claims description 7
- 229920001223 polyethylene glycol Polymers 0.000 claims description 6
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 5
- 229910052760 oxygen Inorganic materials 0.000 claims description 5
- 239000001301 oxygen Substances 0.000 claims description 5
- 229920001451 polypropylene glycol Polymers 0.000 claims description 4
- MTHSVFCYNBDYFN-UHFFFAOYSA-N diethylene glycol Chemical compound OCCOCCO MTHSVFCYNBDYFN-UHFFFAOYSA-N 0.000 claims description 3
- 229920013639 polyalphaolefin Polymers 0.000 claims description 3
- RRQYJINTUHWNHW-UHFFFAOYSA-N 1-ethoxy-2-(2-ethoxyethoxy)ethane Chemical compound CCOCCOCCOCC RRQYJINTUHWNHW-UHFFFAOYSA-N 0.000 claims description 2
- 239000002202 Polyethylene glycol Substances 0.000 claims description 2
- 229940019778 diethylene glycol diethyl ether Drugs 0.000 claims description 2
- ZIBGPFATKBEMQZ-UHFFFAOYSA-N triethylene glycol Chemical compound OCCOCCOCCO ZIBGPFATKBEMQZ-UHFFFAOYSA-N 0.000 claims description 2
- YFNKIDBQEZZDLK-UHFFFAOYSA-N triglyme Chemical compound COCCOCCOCCOC YFNKIDBQEZZDLK-UHFFFAOYSA-N 0.000 claims description 2
- LZDKZFUFMNSQCJ-UHFFFAOYSA-N 1,2-diethoxyethane Chemical compound CCOCCOCC LZDKZFUFMNSQCJ-UHFFFAOYSA-N 0.000 claims 2
- 239000011247 coating layer Substances 0.000 claims 2
- SBZXBUIDTXKZTM-UHFFFAOYSA-N diglyme Chemical compound COCCOCCOC SBZXBUIDTXKZTM-UHFFFAOYSA-N 0.000 claims 1
- 150000003077 polyols Chemical class 0.000 abstract description 9
- 238000004519 manufacturing process Methods 0.000 abstract description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 28
- 229910052799 carbon Inorganic materials 0.000 description 27
- IMNFDUFMRHMDMM-UHFFFAOYSA-N N-Heptane Chemical compound CCCCCCC IMNFDUFMRHMDMM-UHFFFAOYSA-N 0.000 description 18
- 239000000084 colloidal system Substances 0.000 description 15
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 13
- 239000002270 dispersing agent Substances 0.000 description 12
- 239000004215 Carbon black (E152) Substances 0.000 description 7
- 238000013019 agitation Methods 0.000 description 7
- 229930195733 hydrocarbon Natural products 0.000 description 7
- 150000002430 hydrocarbons Chemical class 0.000 description 7
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 6
- 239000012530 fluid Substances 0.000 description 6
- 150000002334 glycols Chemical class 0.000 description 6
- SZVJSHCCFOBDDC-UHFFFAOYSA-N iron(II,III) oxide Inorganic materials O=[Fe]O[Fe]O[Fe]=O SZVJSHCCFOBDDC-UHFFFAOYSA-N 0.000 description 6
- WRIDQFICGBMAFQ-UHFFFAOYSA-N (E)-8-Octadecenoic acid Natural products CCCCCCCCCC=CCCCCCCC(O)=O WRIDQFICGBMAFQ-UHFFFAOYSA-N 0.000 description 5
- LQJBNNIYVWPHFW-UHFFFAOYSA-N 20:1omega9c fatty acid Natural products CCCCCCCCCCC=CCCCCCCCC(O)=O LQJBNNIYVWPHFW-UHFFFAOYSA-N 0.000 description 5
- QSBYPNXLFMSGKH-UHFFFAOYSA-N 9-Heptadecensaeure Natural products CCCCCCCC=CCCCCCCCC(O)=O QSBYPNXLFMSGKH-UHFFFAOYSA-N 0.000 description 5
- 239000005642 Oleic acid Substances 0.000 description 5
- ZQPPMHVWECSIRJ-UHFFFAOYSA-N Oleic acid Natural products CCCCCCCCC=CCCCCCCCC(O)=O ZQPPMHVWECSIRJ-UHFFFAOYSA-N 0.000 description 5
- 238000007792 addition Methods 0.000 description 5
- 238000009835 boiling Methods 0.000 description 5
- 239000000969 carrier Substances 0.000 description 5
- 150000001875 compounds Chemical class 0.000 description 5
- 239000006185 dispersion Substances 0.000 description 5
- 150000002148 esters Chemical class 0.000 description 5
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 description 5
- QXJSBBXBKPUZAA-UHFFFAOYSA-N isooleic acid Natural products CCCCCCCC=CCCCCCCCCC(O)=O QXJSBBXBKPUZAA-UHFFFAOYSA-N 0.000 description 5
- ZQPPMHVWECSIRJ-KTKRTIGZSA-N oleic acid Chemical compound CCCCCCCC\C=C/CCCCCCCC(O)=O ZQPPMHVWECSIRJ-KTKRTIGZSA-N 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 4
- 239000000654 additive Substances 0.000 description 4
- 239000003302 ferromagnetic material Substances 0.000 description 4
- 230000005415 magnetization Effects 0.000 description 4
- 239000002736 nonionic surfactant Substances 0.000 description 4
- 229920000151 polyglycol Polymers 0.000 description 4
- 239000010695 polyglycol Substances 0.000 description 4
- 238000007789 sealing Methods 0.000 description 4
- 239000002002 slurry Substances 0.000 description 4
- 229910017368 Fe3 O4 Inorganic materials 0.000 description 3
- DNIAPMSPPWPWGF-UHFFFAOYSA-N Propylene glycol Chemical compound CC(O)CO DNIAPMSPPWPWGF-UHFFFAOYSA-N 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 3
- 239000000470 constituent Substances 0.000 description 3
- 125000001301 ethoxy group Chemical group [H]C([H])([H])C([H])([H])O* 0.000 description 3
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 3
- 239000003921 oil Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 150000001298 alcohols Chemical class 0.000 description 2
- 125000003545 alkoxy group Chemical group 0.000 description 2
- 125000000129 anionic group Chemical group 0.000 description 2
- 235000013495 cobalt Nutrition 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 235000014113 dietary fatty acids Nutrition 0.000 description 2
- 239000010696 ester oil Substances 0.000 description 2
- 239000000194 fatty acid Substances 0.000 description 2
- 229930195729 fatty acid Natural products 0.000 description 2
- 150000004665 fatty acids Chemical class 0.000 description 2
- 238000000227 grinding Methods 0.000 description 2
- 239000000314 lubricant Substances 0.000 description 2
- 125000000956 methoxy group Chemical group [H]C([H])([H])O* 0.000 description 2
- 229910000069 nitrogen hydride Inorganic materials 0.000 description 2
- 239000003208 petroleum Substances 0.000 description 2
- 229920001281 polyalkylene Polymers 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 229920002545 silicone oil Polymers 0.000 description 2
- 239000000344 soap Substances 0.000 description 2
- 239000006228 supernatant Substances 0.000 description 2
- 239000000725 suspension Substances 0.000 description 2
- 229910000859 α-Fe Inorganic materials 0.000 description 2
- CRWNQZTZTZWPOF-UHFFFAOYSA-N 2-methyl-4-phenylpyridine Chemical compound C1=NC(C)=CC(C=2C=CC=CC=2)=C1 CRWNQZTZTZWPOF-UHFFFAOYSA-N 0.000 description 1
- 239000005695 Ammonium acetate Substances 0.000 description 1
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonium chloride Substances [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 1
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 1
- 239000005977 Ethylene Substances 0.000 description 1
- AVXURJPOCDRRFD-UHFFFAOYSA-N Hydroxylamine Chemical compound ON AVXURJPOCDRRFD-UHFFFAOYSA-N 0.000 description 1
- 229910021578 Iron(III) chloride Inorganic materials 0.000 description 1
- GSEJCLTVZPLZKY-UHFFFAOYSA-N Triethanolamine Chemical compound OCCN(CCO)CCO GSEJCLTVZPLZKY-UHFFFAOYSA-N 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 150000005215 alkyl ethers Chemical class 0.000 description 1
- 150000001412 amines Chemical class 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 229940043376 ammonium acetate Drugs 0.000 description 1
- 235000019257 ammonium acetate Nutrition 0.000 description 1
- 150000003868 ammonium compounds Chemical class 0.000 description 1
- 235000011114 ammonium hydroxide Nutrition 0.000 description 1
- 239000003963 antioxidant agent Substances 0.000 description 1
- 239000008365 aqueous carrier Substances 0.000 description 1
- 239000007900 aqueous suspension Substances 0.000 description 1
- 238000000498 ball milling Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 125000004432 carbon atom Chemical group C* 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 150000001735 carboxylic acids Chemical class 0.000 description 1
- 125000002091 cationic group Chemical group 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 238000001246 colloidal dispersion Methods 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 230000007717 exclusion Effects 0.000 description 1
- 125000005313 fatty acid group Chemical group 0.000 description 1
- 238000009472 formulation Methods 0.000 description 1
- 125000000623 heterocyclic group Chemical group 0.000 description 1
- 125000002636 imidazolinyl group Chemical group 0.000 description 1
- 239000003112 inhibitor Substances 0.000 description 1
- 235000000396 iron Nutrition 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical compound Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 description 1
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 1
- 229910000359 iron(II) sulfate Inorganic materials 0.000 description 1
- 238000005461 lubrication Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 229910001092 metal group alloy Inorganic materials 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 150000007524 organic acids Chemical class 0.000 description 1
- 235000005985 organic acids Nutrition 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 150000003014 phosphoric acid esters Chemical class 0.000 description 1
- 239000002798 polar solvent Substances 0.000 description 1
- 229920000233 poly(alkylene oxides) Polymers 0.000 description 1
- 229920000768 polyamine Polymers 0.000 description 1
- 229920013636 polyphenyl ether polymer Polymers 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 125000002572 propoxy group Chemical group [*]OC([H])([H])C(C([H])([H])[H])([H])[H] 0.000 description 1
- QQONPFPTGQHPMA-UHFFFAOYSA-N propylene Natural products CC=C QQONPFPTGQHPMA-UHFFFAOYSA-N 0.000 description 1
- 125000004805 propylene group Chemical group [H]C([H])([H])C([H])([*:1])C([H])([H])[*:2] 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 150000003856 quaternary ammonium compounds Chemical class 0.000 description 1
- 239000013557 residual solvent Substances 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 239000003381 stabilizer Substances 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- BDHFUVZGWQCTTF-UHFFFAOYSA-M sulfonate Chemical compound [O-]S(=O)=O BDHFUVZGWQCTTF-UHFFFAOYSA-M 0.000 description 1
- 150000003871 sulfonates Chemical class 0.000 description 1
- 230000009974 thixotropic effect Effects 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
- H01B1/20—Conductive material dispersed in non-conductive organic material
- H01B1/24—Conductive material dispersed in non-conductive organic material the conductive material comprising carbon-silicon compounds, carbon or silicon
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16J—PISTONS; CYLINDERS; SEALINGS
- F16J15/00—Sealings
- F16J15/16—Sealings between relatively-moving surfaces
- F16J15/40—Sealings between relatively-moving surfaces by means of fluid
- F16J15/43—Sealings between relatively-moving surfaces by means of fluid kept in sealing position by magnetic force
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
- H01B1/20—Conductive material dispersed in non-conductive organic material
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/44—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of magnetic liquids, e.g. ferrofluids
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/44—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of magnetic liquids, e.g. ferrofluids
- H01F1/442—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of magnetic liquids, e.g. ferrofluids the magnetic component being a metal or alloy, e.g. Fe
Definitions
- U.S. patent application Ser. No. 713,757 describes an electrically conductive ferrofluid composition, which ferrofluid composition comprises a liquid carrier having a colloidal dispersion of ferromagnetic particles in an amount sufficient to provide magnetic properties to the ferrofluid composition and carbon particles in an amount sufficient to provide electrically conductive properties to the ferrofluid composition.
- the ferromagnetic and carbon particles are stabilized in the ferrofluid composition by a surface active dispersing agent.
- the electrically conductive ferrofluid composition is usefully employed in a ferrofluid exclusion seal apparatus to provide an electrically conductive seal apparatus particularly useful for computer disk drives.
- U.S. patent application Ser. No. 736,388 discloses a stable ferrofluid composition and the method of preparing and using the ferrofluid composition, such as in a ferrofluid seal apparatus.
- the ferrofluid composition comprises: a liquid carrier; ferromagnetic particles sufficient to provide magnetic properties to the liquid carrier; and a dispersing amount of a cationic surfactant, such as a quaternary ammonium compound soluble in the carrier, to provide a stable ferrofluid composition.
- the stable ferrofluid compositions have improved electrical conductivity and are useful in sealing computer disk drives.
- U.S. patent application Ser. No. 773,627 describes a low viscosity, electrically conductive ferrofluid composition, which composition comprises a liquid carrier, and contains in combination an electrically conductive amount of a cationic surfactant and dispersed carbon particles, to obtain a low-electrical-resisting ferrofluid having a low viscosity and suitable for use in a ferrofluid bearing apparatus.
- Ferrofluids or magnetic colloids are liquids with magnetic properties in which ferromagnetic materials are colloidally suspended. Such ferrofluids or magnetic liquids must show a high degree of stability (gravitational and magnetic field) in order to perform well in various commercial devices and be responsive to external magnetic fields. Generally a stable magnetic colloid or ferrofluid in a high magnetic field gradient require small ferromagnetic particles of generally less than 100 angstroms in diameter. The ferromagnetic particles are typically coated with one or several separate layers of surfactants to prevent agglomeration in any particular liquid carrier.
- Ferrofluids are widely known and used, and typical ferrofluid compositions are described, for example, in U.S. Pat. No. 3,700,595, issued Oct. 24, 1972, wherein anionic surfactants, such as fatty acids, alcohols, amines or amids and other organic acids are employed as dispersing surface active agents; U.S. Pat. No. 3,764,504, issued Oct. 9, 1973, wherein aliphatic monocarboxylic acids are employed as dispersing agents; U.S. Pat. No. 4,208,294, issued June 17, 1980, wherein a water based magnetic liquid is produced by the employment of C 10 to C 15 aliphatic monocarboxylic acids as acid dispersing agents; and U.S. Pat. No. 4,430,239, issued Feb. 7, 1984, wherein a stable ferrofluid composition is provided employing a phosphoric acid ester of a long-chain alcohol as a surfactant.
- anionic surfactants such as fatty acids, alcohols, amines or amid
- ferrofluid compositions composed of a silicone-oil carrier and a dispersing amount of an anionic surfactant which forms a chemical bond with the surface of the magnetic particles as a tail group compatible or suitable in the silicone-oil carrier; and U.S. Pat. No. 4,485,024, issued Nov. 27, 1984, wherein a ferrofluid is produced through controlling the pH of the aqueous suspension of the ferromagnetic particles of an organic solvent together with surface active agents, such as fatty carboxylic acids.
- a properly stabilized ferrofluid composition typically undergoes practically no aging or separation, remains liquid in a magnetic field and after removing of the magnetic field shows no hysteresis.
- Such a stabilized ferrofluid exhibits stability by overcoming generally three principal attractive forces: van der Waals, interparticles--magnetic and gravitational forces.
- the average particle needed in a ferrofluid depends on the selection of the ferromagnetic materials and typically may range from 20 to 300 angstroms, for example 20 to 200 angstroms, and for use in a very high magnetic field gradient may range up to 100 angstroms in diameter.
- the ferromagnetic particles must be covered by one or more layers of the selected surfactant in order to provide stability in an external magnetic field gradient.
- ferrofluid compositions have been used in a wide variety of commercial applications, such as for ferromagnetic seals, as dampening liquids in inertia dampers, as heat transfer liquids in the voice coil of loudspeakers, as bearing liquids, as ferrolubricants, for domain detection, for all prospecting, and other applications.
- Electrically conductive ferrofluid compositions are usually employed in computer disk drive applications, for example to provide a conventional sealing ring, and further for the conduction of electrical charges from the shaft so as to prevent charge build up on the disk.
- the static charge build up at the disk in a rotating spindle needs to be grounded in addition to sealing hermetically the disk cavity for contamination-free operation.
- Electrically conductive ferrofluids which contain finely divided dispersed carbon particles are quite useful; however, there is a need to restrict the amount of carbon black employed in the ferrofluid compositions to avoid gradual increases in the viscosity of the composition and absorption of the fluid into the carbon particles with time.
- carbon black to a typical ferrofluid composition provides for a composition which tends to be pseudoplastic in amounts greater than about 5 percent of carbon black, while low concentrations of carbon black provide for a Newtonian composition. Therefore, it is desirable to provide for stable, low viscosity, highly electrically conductive ferrofluid compositions both with or without the use of carbon black, and particularly for use in the computer seal, as well as other devices wherein a stable, low viscosity, highly electrically conductive ferrofluid composition is useful.
- the present invention concerns low viscosity, stable, electrically conductive ferrofluid compositions and the method of preparing and using such compositions, such as for example as a ferrolubricant and bearing apparatus and as a ferrofluid composition in seals.
- the invention relates to a ferrofluid composition which includes a dissociation or ionization liquid agent for the dissociation and ionization of the surfactant employed in the ferrofluid composition to disperse the magnetic particles.
- the electrically conductive, low viscosity, stable ferrofluid composition comprises: a first polar liquid carrier, typically a low viscosity, nonvolatile-type liquid carrier; an agent which is miscible or soluble in the polar liquid carrier; magnetic particles dispersed in the liquid carriers in a sufficient amount to provide for the desired magnetic properties of the ferrofluid composition; and a surfactant, such as, for example, but not limited to, a cationic surfactant which acts as a dispersing agent for the ferromagnetic particles or other particles in the ferrofluid composition and which also helps to provide for electrical conductivity properties in the composition.
- a surfactant such as, for example, but not limited to, a cationic surfactant which acts as a dispersing agent for the ferromagnetic particles or other particles in the ferrofluid composition and which also helps to provide for electrical conductivity properties in the composition.
- the polar agent employed in the ferrofluid composition is selected to provide for dissociation or ionization of the surfactant.
- the agent or liquid carrier comprises an oxygen-containing compound, such as for example, a polyol compound, such as a polyol ether and more particularly a glycol ether, so as to provide for dissociation of the surfactant.
- the ferrofluid composition may include dispersed carbon particles in the ferrofluid composition, typically in an amount so as not to provide for a substantial increase in ferrofluid viscosity, since the addition of the carbon particles further increases the electrical conductivity of the composition.
- the ferrofluid composition may also include controlled amounts of dispersed carbon particles, such as finely divided carbon black, which in combination particularly with a cationic surfactant and the polyol ether provides for a very stable, but low electrical conductivity ferrofluid.
- dispersed carbon particles such as finely divided carbon black
- a cationic surfactant and the polyol ether provides for a very stable, but low electrical conductivity ferrofluid.
- the liquid carrier employed in the preparation of the ferrofluid composition may be any type of a liquid polar carrier and typically is a stable, nonvolatile liquid, for example but not limited to: fluorocarbons; amino-alcohol; polyphenyl ethers; polyglycols; amido-amines; esters; polyolesters; glycol esters; and various other esters, such as for example, and more particularly, a polyol ester oil liquid or a polyalphaolefin base.
- the polar liquid carrier, as well as the second polar liquid agent, employed may contain or have various additives, such as stabilizers, antioxidants, corrosion inhibitors, viscosity index additives, or various minor amounts of other additives to improve the selected quality or property of the ferrofluid composition.
- the magnetic particles employed in the ferrofluid compositions may be those magnetic-type of particles commonly employed in preparing ferrofluid compositions and typically comprise finely divided single domain particles of ferromagnetic materials, such as, but not to be limited to: magnetite; ferrites; iron; nickel; cobalt; metal carbides or metal oxides; metal alloys; and other finely divided materials which have or can be made to have magnetic properties when dispersed in a liquid carrier.
- ferromagnetic particle comprises magnetite particles.
- the ferromagnetic particles employed are finely divided and are generally less than 1000 angstroms, but more typically less than 300 angstroms, such as for example about 20 to 200 angstroms in single domain particles.
- the ferromagnetic particles are dispersed and stabilized and used in combination with the employment of a dispersing agent or surfactant, typically any surfactant may be employed, such as a nonionic, cationic or anionic surfactant. However, it is desirable to employ a cationic surfactant in order to provide for increased or improved electrical conductivity.
- a dispersing agent or surfactant typically any surfactant may be employed, such as a nonionic, cationic or anionic surfactant.
- a cationic surfactant in order to provide for increased or improved electrical conductivity.
- the amount and nature of the surfactant employed may vary depending on the particular liquid carriers used, the ferromagnetic particles and the size thereof, and the type and stability of the dispersion desired.
- the ratio of the surfactant as a dispersing agent to the ferromagnetic particles may vary, but generally in the ferrofluid composition ranges from about 0.5:1 to 20:1 by weight, with the ferromagnetic particles generally present in the composition in an amount ranging from 5 to about 80 percent by weight of the liquid carrier.
- the ferrofluid compositions prepared have varying saturization and magnetization values, and typically range from 20 to 800 gauss, for example 100 to 500 gauss, and range in viscosity from about 25 cp to 5000 cp.
- Particularly preferred cationic surfactants comprise: the quaternary ammonium surfactant molecules, generally with two structural parts; a polar head group comprising the quaternary ammonium which attaches to the ferromagnetic particle surface or to a layer of another surfactant; and a tail group with properties similar to the surrounding fluid matrix or the polar carrier liquids, and typically being compatible with and soluble in the organic liquid carrier.
- the selection of the particular tail group of the quaternized ammonium surfactant should be matched with the particular polar liquid carrier employed, for example a hydrocarbon tail group of a quaternized ammonium compound would typically be soluble in hydrocarbon oil or polyalphaolefin nonpolar-type organic liquid carriers, while tail groups having a hydroxyl or an oxygen-containing tail, e.g. OH groups, would be soluble and compatible in glycols, polyglycols, esters, esterglycols and the like.
- a polyalkylene oxide such as a polypropylene oxide tail group of a quaternized ammonium cationic surfactant
- a polar organic liquid carrier such as esters, polyol esters, polyglycols or glycolesters.
- cationic surfactants as dispersing agents permits the dispersing of ferromagnetic particles in an entirely new family of organic liquid carriers or lubricants, such as polyol esters, glycols, silahydrocarbons and various other organic liquid carriers which may be used as oils, lubricants, bearing fluids and the like.
- Cationic surfactants which are insoluble in water also allow the possibility of making ferrofluid compositions of magnetic colloids compatible with water or alcohols.
- the ferrofluids employing cationic surfactants may be used in all known applications of ferrofluids, such as sealing, dampening, lubrication, heat transfer, domain detection, bearing fluids, and in other applications.
- cationic surfactants may be employed as the dispersing agent of the invention where the tail portion of the surfactant molecule is soluble in or compatible with the carrier liquid, and in addition is of sufficient length in order to provide a stable ferrofluid composition, for example, typically the length of the molecular structure of the tail portion of the cationic surfactant should be more than about 20 angstroms to stabilize particles having a diameter of about 100 angstroms or more.
- the particularly preferred cationic surfactants of the invention comprise the quaternary ammonium cationic surfactant composed of a quaternary ammonium head group and a long tail portion, such as for example, ranging in each surfactant molecule from about 10 to 50 angstroms in overall length or having C 6 -C 30 , e.g. C 8 -C 18 , carbon atoms or length.
- Some quaternary ammonium cationic surfactants useful as dispersing agents in the ferrofluid composition would comprise, but not be limited to the following representative classes, such as: quaternary imidazoline salts which contain a heterocyclic ring which contains a quaternary ammonium group and includes a long chain, such as a fatty acid substituent group; aliphatic quaternary ammonium salts where at least one of the groups and often two of the groups through the quaternary ammonium and nitrogen comprises a long chain group, such as a fatty acid group; and quaternary acylated polyamine salts which contain, for example, a long chain alkoxy group such as an ethoxy or propoxy group, which compounds are particularly useful as dispersing agents where the liquid carrier comprises an oxygen-containing liquid, such as an ester, glycol or polyol ester.
- the cationic surfactant should be employed in an amount sufficient to provide for a stable dispersion, and may be used alone or in combination with other surfactants, such as nonionic surfactants (but not directly with anionic surfactants), and with other various additives or used in combination.
- the carbon particles employed in the ferrofluid composition can be derived from any carbon material; however, it has been found that the best electrical conductivity is obtained by dispersing electrically conductive carbon black particles having a particle size of about 50 to 300 angstroms and a surface area of about 100 to 3000 meters per square gram, such carbon black particles are typically produced by various processes.
- the carbon black derived from the furnace process is particularly useful.
- the agent employed is typically a high molecular weight, high boiling point, for example of over 250° C., low evaporation, oxygen-containing liquid which dissociates the surfactant or ionizes the surfactant.
- the surfactant selected which is dissociated may be one or more of the surfactants used in the ferrofluid composition and is present in excess quantity and should be dissociated by the polar agent, and more particularly dissociated or ionized by hydroxyl-type groups, or alkoxy-type groups, such as ethoxy and methoxy groups.
- a polar agent which provides for such dissociation and ionization permits the preparation of low viscosity ferrofluid compositions having electrical resistivity of less than generally about 1 ⁇ 10 7 and in combination with amounts of up to 5 percent of carbon particles with electrical conductivity of less than 1 ⁇ 10 6 ohms-centimeter.
- the resistivity was found to depend on temperature more dramatically with carbon present than in the absence of carbon.
- the polar agent employed should have one, and preferably two or more, hydroxyls or ethoxy or methoxy groups, typically separated by hydrocarbon or other alkoxy groups and must be miscible with the first liquid polar carrier.
- the polar agent may comprise for instance a polyol, such as glycol, and more particularly polyethylene and polypropylene glycols. While ethylene glycol and propylene glycol may be suitable, particularly in small amounts, they are not generally preferred in that they evaporate at too low a temperature and therefore limit the life of the ferrofluid compositions.
- the low molecular weight glycols provide higher conductivity values for the ferrofluid compared with the higher molecular weight glycols.
- the polar agent are those alkyl ether compounds of polyalkylene polyols, and more particularly the lower alkyl ethers of such compounds wherein the polyalkylene comprises an ethylene or propylene.
- Particularly preferred compounds for use in the invention would include the di-, tri- and tetraethylene glycol dialkyl ethers and particularly those having a boiling point about 200° C., and more particularly about 250° C.
- Suitable specific compounds include, but not to be limited to: the diethylene glycol dibutyl ether; the tetraethylene glycol dimethyl ether, as well as triethylene glycol dimethyl ether and a lower boiling point diethylene glycol diethyl ether, as well as various low molecular weight liquid polyethylene and polypropylene glycol compounds, such as polyethylene glycol having molecular weights ranging from about 400-800.
- the ferrofluid composition may be prepared employing the usual and generally accepted techniques of ball milling and grinding, or precipitation as in the prior art, to prepare the ferrofluid compositions.
- the cationic surfactants may be used in conjunction with anionic and nonionic surfactants or may be used as one surfactant layer; while other surfactants, anionic, nonionic or other cationic surfactants, may be used in another layer or to complete the first layer.
- the ferromagnetic particles may be dispersed first with an anionic surfactant, and then a separate surfactant to complete the layer or as a second layer of a cationic surfactant is employed, or vice versa, to provide stable ferrofluid compositions.
- the stable ferrofluid composition may comprise cationic surfactants together with other surfactants, typically a first dispersing layer of an anionic fatty acid surfactant followed by a final dispersing of the anionic surfactant magnetic particles with a cationic surfactant or other surfactant which can be dissociated.
- the resistivity will be high, while for example where the carbon particles are less than 100 angstroms; however, carbon particles may be employed in clusters or aggregates, for example over 1000 angstroms, in which case the resistivity will be low.
- the carbon particles may be employed in aggregate form and it is not needed to be broken up, or may be employed in individual particle broken up aggregates.
- Ferrofluid compositions of improved electrical conductivity may comprise, for example, general formulations as follows:
- Ferromagnetic particles such as Fe 3 O4, about 3-7 percent by volume, for example 5 percent;
- Carbon black coated particles with any of the constituents of ferrofluid to minimize absorption from the furnace process 100 angstroms or less, about 1-6 percent by volume, for example about 2.5 percent by volume;
- Polar liquid carrier that is the dissociation or ionization agent, from about 3-20 percent by volume, more particularly 5-12 percent;
- First surfactant typically an anionic surfactant, such as oleic acid, for precoating the ferromagnetic particles in an amount of from 5-10 percent by volume, for example 5 percent;
- Second surfactant preferably a cationic surfactant, such as a quaternary ammonium surfactant, and more particularly a quaternary ammonium alkoxyl surfactant, from about 2-12 percent by volume, and typically 5 percent.
- a cationic surfactant such as a quaternary ammonium surfactant, and more particularly a quaternary ammonium alkoxyl surfactant, from about 2-12 percent by volume, and typically 5 percent.
- the magnetite (Fe 3 O4) particles were prepared using 240 grams of FeSO 4 , 425 ml of 45 percent FeCl 3 and 600 ml water. The solid components were well dissolved in water at 5° to 70° C. under constant agitation.
- Fe 3 O 4 was precipitated from the above solution by the slow addition of ammonia solution 30 percent NH 3 to reach the pH of 12. 100 ml of soap is added under a strong agitation.
- the soap composition is oleic acid (or isosteric acid):ammonia (30 percent NH 3 ) solution in volume ratio of 1:1.
- the suspension of magnetite particles covered with oleic acid is mixed for 30 minutes at 50°-90° C., then 350 cc of an Isoparaffinic hydrocarbon fraction (ISOPAR-G having a boiling point range of 160° to 176° C. of Exxon Chemical Co.) is added to the suspension under constant agitation.
- Isoparaffinic hydrocarbon fraction ISOPAR-G having a boiling point range of 160° to 176° C. of Exxon Chemical Co.
- the acetone wet slurry was added in a beaker containing 500 cc of heptane. Under the strong agitation, the slurry was heated to 80° C. in order to remove the acetone.
- the remaining fluid is 450 cc heptane based magnetic colloid having approximately 400 gauss saturated magnetization.
- a total of 120 grams of a polypropoxy quaternary ammonium acetate surfactant (EMCOL CC55 of WITCO Chemical Co.) was added to the heptane base magnetic colloid at 70° C. under constant stirring. Prior to using EMCOL CC55, it was cleaned in a vacuum chamber by continuous pumping for 24 hours. By this process, residual solvents present in the surfactant were removed. The surfactant amount is sufficient to provide a stable colloid and to suspend subsequent addition of carbon particles and to provide the necessary ionization to electrical conductivity. After 30 minutes of agitation at 70° C., the adsorption of the second surfactant was considered complete.
- EMCOL CC55 polypropoxy quaternary ammonium acetate surfactant
- a total of 300 cc of liquid carrier of Polyolester (Mobil Ester P-42, having a pour point of -51° C., flash point 243° C. and viscosity index of 134) of Mobil Chemical Co. was added under the agitation to the heptane base magnetic colloid.
- the mixture was held at 100° C. until all the heptane was removed.
- the ferrofluid was kept in high magnetic field gradient at 80° C. for 24 hours in order to remove the large aggregates.
- the supernatant fluid was filtered and the final magnetic colloid was 350 gauss and 60 cp viscosity at 27° C.
- Conductex 40-220 carbon black particles (Columbia Chemicals Company) are added to a 100 cc mixture of heptane and polyolester P-42 (30 percent P-42 in heptane) and mixed thoroughly for 60 minutes. The heptane was removed at 100° C. in 72 hours. The polyolester oil was absorbed on carbon black. The carbon black slurry was kept at 100° C. in vacuum oven (30 inch vacuum) for another 24 hours at 100° C. to thoroughly remove the heptane. The carbon particles may also be coated with a glycol the same way or with a cationic surfactant.
- the magnetic colloid having 350 gauss was diluted down to 250 gauss using a mixture of Tetraglyme, a tetraethylene glycol dimethyl ether, (boiling point 275° C. of Ferro Corp.) and a polyol glycol (POLYOL P-425 of Dow Chemical Company).
- the mixture consisting of 50 percent glymes (organic compounds in the family of symmetrical glycol diethers) and 45 percent Polyglycol P-425 and 5 percent of triethanolamine. This mixture acts as a strong polar solvent for the cationic surfactant CC55 in final electrically conductive ferrofluid.
- the electrically conducting magnetic ferrofluid thus prepared was tested and had a 250 gauss saturation magnetization and an electrical resistivity of about 10 7 ohm-cm.
- the carbon black particles optionally employed in the ferrofluid composition were precoated with a polyol ester oil. Where carbon black particles are not coated, the electrical conductivity is generally lower than that obtained in Example 1.
- the precoating of the carbon black particles has been found to be important in order to prevent gradual increases in viscosity in the ferrofluid composition. Thus, where carbon particles are employed, the carbon particles should be precoated with any of the constituents of ferrofluid and then introduced into the ferrofluid composition.
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Chemical & Material Sciences (AREA)
- Dispersion Chemistry (AREA)
- Spectroscopy & Molecular Physics (AREA)
- General Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Mechanical Engineering (AREA)
- Soft Magnetic Materials (AREA)
- Lubricants (AREA)
Abstract
Description
Claims (13)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US07/054,412 US4732706A (en) | 1985-03-20 | 1987-05-26 | Method of preparing low viscosity, electrically conductive ferrofluid composition |
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US06/713,757 US4604229A (en) | 1985-03-20 | 1985-03-20 | Electrically conductive ferrofluid compositions and method of preparing and using same |
US06/875,985 US4687596A (en) | 1985-03-20 | 1986-06-19 | Low viscosity, electrically conductive ferrofluid composition and method of making and using same |
US07/054,412 US4732706A (en) | 1985-03-20 | 1987-05-26 | Method of preparing low viscosity, electrically conductive ferrofluid composition |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US06/875,985 Division US4687596A (en) | 1985-03-20 | 1986-06-19 | Low viscosity, electrically conductive ferrofluid composition and method of making and using same |
Publications (1)
Publication Number | Publication Date |
---|---|
US4732706A true US4732706A (en) | 1988-03-22 |
Family
ID=27368636
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US07/054,412 Expired - Lifetime US4732706A (en) | 1985-03-20 | 1987-05-26 | Method of preparing low viscosity, electrically conductive ferrofluid composition |
Country Status (1)
Country | Link |
---|---|
US (1) | US4732706A (en) |
Cited By (26)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4929376A (en) * | 1988-03-23 | 1990-05-29 | Dow Corning Corporation | Quaternary ammonium salt of an alkoxysilane as a dispersant for magnetic pigment |
US4944802A (en) * | 1988-09-16 | 1990-07-31 | Omni Quest Corporation | High coercivity magnetic inks and method for making same |
US4961959A (en) * | 1988-03-23 | 1990-10-09 | Dow Corning Corporation | Quaternary ammonium salt of an alkoxysilane as a dispersant for magnetic pigment |
US5104582A (en) * | 1988-10-18 | 1992-04-14 | Skf Nova Ab | Electrically conductive fluids |
US5354488A (en) * | 1992-10-07 | 1994-10-11 | Trw Inc. | Fluid responsive to a magnetic field |
US5465810A (en) * | 1994-10-07 | 1995-11-14 | Mobil Oil Corporation | Multi-phase lubricant and apparatus for the dispensing thereof |
US5485895A (en) * | 1994-10-07 | 1996-01-23 | Mobil Oil Corporation | Multi-phase lubricant process for lubricating with multi-phase lubricants |
US5602085A (en) * | 1994-10-07 | 1997-02-11 | Mobil Oil Corporation | Multi-phase lubricant |
US5645752A (en) * | 1992-10-30 | 1997-07-08 | Lord Corporation | Thixotropic magnetorheological materials |
US5660397A (en) * | 1994-09-23 | 1997-08-26 | Holtkamp; William H. | Devices employing a liquid-free medium |
DE19654864A1 (en) * | 1996-02-27 | 1997-08-28 | Thomas Dipl Ing Haehndel | Magnetofluid with a saturation magnetization of 150 to 450 mT |
US5843579A (en) * | 1996-06-27 | 1998-12-01 | Ncr Corporation | Magnetic thermal transfer ribbon with aqueous ferrofluids |
US5863455A (en) * | 1997-07-14 | 1999-01-26 | Abb Power T&D Company Inc. | Colloidal insulating and cooling fluid |
US20020125790A1 (en) * | 2000-07-11 | 2002-09-12 | Robert Horning | MEMS actuator with lower power consumption and lower cost simplified fabrication |
US20030155827A1 (en) * | 2002-02-19 | 2003-08-21 | Innovative Technology Licensing, Llc | Multiple magnet transducer |
US20030155771A1 (en) * | 2002-02-19 | 2003-08-21 | Innovative Technology Licensing, Llc | Electrical generator with ferrofluid bearings |
WO2003071143A2 (en) * | 2002-02-19 | 2003-08-28 | Rockwell Scientific Licensing, Llc. | Mechanical translator with ultra low friction ferrofluid bearings |
US20040155228A1 (en) * | 2003-02-05 | 2004-08-12 | Metallux Gmbh | Electrically conducting, magnetic powder |
DE10304794A1 (en) * | 2003-02-05 | 2004-09-09 | Metallux Gmbh | Electrically conducting, magnetic powder for electrical part for transmitting electrical signal/voltage/current between contacts contains or consists of electrically conducting and magnetic particles |
US6798090B2 (en) | 2002-04-18 | 2004-09-28 | Rockwell Scientific Licensing, Llc | Electrical power generation by coupled magnets |
US6812598B2 (en) | 2002-02-19 | 2004-11-02 | Rockwell Scientific Licensing, Llc | Multiple magnet transducer with differential magnetic strengths |
US20040217324A1 (en) * | 2003-05-02 | 2004-11-04 | Henry Hsu | Magnetorheological fluid compositions and prosthetic knees utilizing same |
US20040251750A1 (en) * | 2002-02-19 | 2004-12-16 | Rockwell Scientific Licensing, Llc | Magnetic transducer with ferrofluid end bearings |
US20050258090A1 (en) * | 2004-05-21 | 2005-11-24 | Crosby Gernon | An electromagnetic rheological (emr) fluid and method for using the emr fluid |
US20140028117A1 (en) * | 2012-07-27 | 2014-01-30 | Vytautas Bucinskas | Chaotic vibration energy harvester and method for controlling same |
US8841232B1 (en) | 2013-12-13 | 2014-09-23 | Lucian Borduz | Advanced ceramic catalyst |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3764540A (en) * | 1971-05-28 | 1973-10-09 | Us Interior | Magnetofluids and their manufacture |
US4430239A (en) * | 1981-10-21 | 1984-02-07 | Ferrofluidics Corporation | Ferrofluid composition and method of making and using same |
US4469624A (en) * | 1982-05-20 | 1984-09-04 | Asahi Kasei Kogyo Kabushiki Kaisha | Magnetic coating compositions for magnetic recording materials |
US4604229A (en) * | 1985-03-20 | 1986-08-05 | Ferrofluidics Corporation | Electrically conductive ferrofluid compositions and method of preparing and using same |
US4687596A (en) * | 1985-03-20 | 1987-08-18 | Ferrofluidics Corporation | Low viscosity, electrically conductive ferrofluid composition and method of making and using same |
-
1987
- 1987-05-26 US US07/054,412 patent/US4732706A/en not_active Expired - Lifetime
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3764540A (en) * | 1971-05-28 | 1973-10-09 | Us Interior | Magnetofluids and their manufacture |
US4430239A (en) * | 1981-10-21 | 1984-02-07 | Ferrofluidics Corporation | Ferrofluid composition and method of making and using same |
US4469624A (en) * | 1982-05-20 | 1984-09-04 | Asahi Kasei Kogyo Kabushiki Kaisha | Magnetic coating compositions for magnetic recording materials |
US4604229A (en) * | 1985-03-20 | 1986-08-05 | Ferrofluidics Corporation | Electrically conductive ferrofluid compositions and method of preparing and using same |
US4687596A (en) * | 1985-03-20 | 1987-08-18 | Ferrofluidics Corporation | Low viscosity, electrically conductive ferrofluid composition and method of making and using same |
Cited By (47)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4961959A (en) * | 1988-03-23 | 1990-10-09 | Dow Corning Corporation | Quaternary ammonium salt of an alkoxysilane as a dispersant for magnetic pigment |
US4929376A (en) * | 1988-03-23 | 1990-05-29 | Dow Corning Corporation | Quaternary ammonium salt of an alkoxysilane as a dispersant for magnetic pigment |
US4944802A (en) * | 1988-09-16 | 1990-07-31 | Omni Quest Corporation | High coercivity magnetic inks and method for making same |
US5104582A (en) * | 1988-10-18 | 1992-04-14 | Skf Nova Ab | Electrically conductive fluids |
US5354488A (en) * | 1992-10-07 | 1994-10-11 | Trw Inc. | Fluid responsive to a magnetic field |
US5645752A (en) * | 1992-10-30 | 1997-07-08 | Lord Corporation | Thixotropic magnetorheological materials |
US5660397A (en) * | 1994-09-23 | 1997-08-26 | Holtkamp; William H. | Devices employing a liquid-free medium |
US5704613A (en) * | 1994-09-23 | 1998-01-06 | Holtkamp; William H. | Methods for sealing and unsealing using a magnetically permeable solid-based medium |
US5602085A (en) * | 1994-10-07 | 1997-02-11 | Mobil Oil Corporation | Multi-phase lubricant |
US5485895A (en) * | 1994-10-07 | 1996-01-23 | Mobil Oil Corporation | Multi-phase lubricant process for lubricating with multi-phase lubricants |
US5465810A (en) * | 1994-10-07 | 1995-11-14 | Mobil Oil Corporation | Multi-phase lubricant and apparatus for the dispensing thereof |
DE19654864A1 (en) * | 1996-02-27 | 1997-08-28 | Thomas Dipl Ing Haehndel | Magnetofluid with a saturation magnetization of 150 to 450 mT |
US5843579A (en) * | 1996-06-27 | 1998-12-01 | Ncr Corporation | Magnetic thermal transfer ribbon with aqueous ferrofluids |
US5863455A (en) * | 1997-07-14 | 1999-01-26 | Abb Power T&D Company Inc. | Colloidal insulating and cooling fluid |
US20020125790A1 (en) * | 2000-07-11 | 2002-09-12 | Robert Horning | MEMS actuator with lower power consumption and lower cost simplified fabrication |
US20040155467A1 (en) * | 2002-02-19 | 2004-08-12 | Innovative Technology Licensing, Llc | Electrical generator with ferrofluid bearings |
USRE41626E1 (en) * | 2002-02-19 | 2010-09-07 | Teledyne Licensing, Llc | Multiple magnet transducer with differential magnetic strengths |
WO2003071664A1 (en) * | 2002-02-19 | 2003-08-28 | Rockwell Scientific Licensing, Llc | Multiple magnet transducer |
WO2003071143A2 (en) * | 2002-02-19 | 2003-08-28 | Rockwell Scientific Licensing, Llc. | Mechanical translator with ultra low friction ferrofluid bearings |
WO2003071143A3 (en) * | 2002-02-19 | 2003-12-18 | Rockwell Scient Licensing Llc | Mechanical translator with ultra low friction ferrofluid bearings |
US20040130422A1 (en) * | 2002-02-19 | 2004-07-08 | Rockwell Scientific Licensing, Llc | Mechanical translator with ultra low friction ferrofluid bearings |
US6768230B2 (en) | 2002-02-19 | 2004-07-27 | Rockwell Scientific Licensing, Llc | Multiple magnet transducer |
US20030155827A1 (en) * | 2002-02-19 | 2003-08-21 | Innovative Technology Licensing, Llc | Multiple magnet transducer |
US20030155771A1 (en) * | 2002-02-19 | 2003-08-21 | Innovative Technology Licensing, Llc | Electrical generator with ferrofluid bearings |
CN1333177C (en) * | 2002-02-19 | 2007-08-22 | 洛克威尔科学许可有限公司 | Mechanical translator with ultra low friction ferrofluid bearings |
US6917131B2 (en) | 2002-02-19 | 2005-07-12 | Rockwell Scientific Licensing, Llc | Transverse mechanical translator with ferrofluid support |
US6809427B2 (en) | 2002-02-19 | 2004-10-26 | Rockwell Scientific Licensing, Llc | Electrical generator with ferrofluid bearings |
US6812583B2 (en) | 2002-02-19 | 2004-11-02 | Rockwell Scientific Licensing, Llc | Electrical generator with ferrofluid bearings |
US6812598B2 (en) | 2002-02-19 | 2004-11-02 | Rockwell Scientific Licensing, Llc | Multiple magnet transducer with differential magnetic strengths |
US7288860B2 (en) | 2002-02-19 | 2007-10-30 | Teledyne Licensing, Inc. | Magnetic transducer with ferrofluid end bearings |
US20040251750A1 (en) * | 2002-02-19 | 2004-12-16 | Rockwell Scientific Licensing, Llc | Magnetic transducer with ferrofluid end bearings |
US6833780B2 (en) | 2002-02-19 | 2004-12-21 | Rockwell Scientific Licensing, Llc | Mechanical translator with ultra low friction ferrofluid bearings |
US20050023906A1 (en) * | 2002-02-19 | 2005-02-03 | Rockwell Scientific Licensing, Llc | Transverse mechanical translator with ferrofluid support |
US6861772B2 (en) | 2002-02-19 | 2005-03-01 | Rockwell Scientific Licensing, Llc | Multiple magnet system with different magnet properties |
US6798090B2 (en) | 2002-04-18 | 2004-09-28 | Rockwell Scientific Licensing, Llc | Electrical power generation by coupled magnets |
US20040155228A1 (en) * | 2003-02-05 | 2004-08-12 | Metallux Gmbh | Electrically conducting, magnetic powder |
DE10304794B4 (en) * | 2003-02-05 | 2007-06-06 | Metallux Ag | Use of an electrically conductive, magnetic fluid |
DE10304794A1 (en) * | 2003-02-05 | 2004-09-09 | Metallux Gmbh | Electrically conducting, magnetic powder for electrical part for transmitting electrical signal/voltage/current between contacts contains or consists of electrically conducting and magnetic particles |
US20060178753A1 (en) * | 2003-05-02 | 2006-08-10 | Henry Hsu | Magnetorheological fluid compositions and prosthetic knees utilizing same |
US7101487B2 (en) | 2003-05-02 | 2006-09-05 | Ossur Engineering, Inc. | Magnetorheological fluid compositions and prosthetic knees utilizing same |
US20060197051A1 (en) * | 2003-05-02 | 2006-09-07 | Henry Hsu | Magnetorheological fluid compositions and prosthetic knees utilizing same |
US20040217324A1 (en) * | 2003-05-02 | 2004-11-04 | Henry Hsu | Magnetorheological fluid compositions and prosthetic knees utilizing same |
US7335233B2 (en) | 2003-05-02 | 2008-02-26 | Ossur Hf | Magnetorheological fluid compositions and prosthetic knees utilizing same |
US20050258090A1 (en) * | 2004-05-21 | 2005-11-24 | Crosby Gernon | An electromagnetic rheological (emr) fluid and method for using the emr fluid |
US7422709B2 (en) | 2004-05-21 | 2008-09-09 | Crosby Gernon | Electromagnetic rheological (EMR) fluid and method for using the EMR fluid |
US20140028117A1 (en) * | 2012-07-27 | 2014-01-30 | Vytautas Bucinskas | Chaotic vibration energy harvester and method for controlling same |
US8841232B1 (en) | 2013-12-13 | 2014-09-23 | Lucian Borduz | Advanced ceramic catalyst |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US4687596A (en) | Low viscosity, electrically conductive ferrofluid composition and method of making and using same | |
US4732706A (en) | Method of preparing low viscosity, electrically conductive ferrofluid composition | |
US4604222A (en) | Stable ferrofluid composition and method of making and using same | |
US4604229A (en) | Electrically conductive ferrofluid compositions and method of preparing and using same | |
US5147573A (en) | Superparamagnetic liquid colloids | |
US4356098A (en) | Stable ferrofluid compositions and method of making same | |
EP0206516A2 (en) | Ferrofluid composition, method of making, and apparatus and method using same | |
US5167850A (en) | Fluid responsive to magnetic field | |
US5645752A (en) | Thixotropic magnetorheological materials | |
EP0856189B1 (en) | Aqueous magnetorheological materials | |
US4867910A (en) | Electrically conductive ferrofluid composition | |
US5714084A (en) | Electrorheological magnetic fluid and process for producing the same | |
CA2146551A1 (en) | Magnetorheological materials based on alloy particles | |
EP1609160A1 (en) | Magnetic fluid having an improved chemical stability and process for preparing the same | |
US6261471B1 (en) | Composition and method of making a ferrofluid having an improved chemical stability | |
US5085789A (en) | Ferrofluid compositions | |
EP0797832B1 (en) | Ferrofluid having improved oxidation resistance | |
US6068785A (en) | Method for manufacturing oil-based ferrofluid | |
US5135672A (en) | Electroconductive magnetic fluid composition and process for producing the same | |
EP0406692B1 (en) | Fluid responsive to a magnetic field | |
US5094767A (en) | Highly viscous magnetic fluids having nonmagnetic particles | |
JPS63232402A (en) | Conductive magnetic fluid composition and manufacture thereof | |
EP0579229B1 (en) | Fluid having magnetic and electrorheological effects simultaneously | |
JPS63280403A (en) | Conductive magnetic fluid compositing and manufacture thereof | |
WO1990015423A1 (en) | Superparamagnetic liquid colloids |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
STCF | Information on status: patent grant |
Free format text: PATENTED CASE |
|
AS | Assignment |
Owner name: FLEET NATIONAL BANK, RHODE ISLAND Free format text: SECURITY INTEREST;ASSIGNOR:FERROFLUIDICS CORPORATION, A CORP MA;REEL/FRAME:005481/0243 Effective date: 19901013 |
|
FPAY | Fee payment |
Year of fee payment: 4 |
|
REFU | Refund |
Free format text: REFUND PROCESSED. MAINTENANCE FEE HAS ALREADY BEEN PAID (ORIGINAL EVENT CODE: R160); ENTITY STATUS OF PATENT OWNER: SMALL ENTITY |
|
FPAY | Fee payment |
Year of fee payment: 8 |
|
FPAY | Fee payment |
Year of fee payment: 12 |
|
SULP | Surcharge for late payment | ||
AS | Assignment |
Owner name: FERROTEC (USA) CORPORATION, NEW HAMPSHIRE Free format text: CHANGE OF NAME;ASSIGNOR:FERROFLUIDICS CORPORATION;REEL/FRAME:014201/0096 Effective date: 20010716 |
|
FEPP | Fee payment procedure |
Free format text: PAYOR NUMBER ASSIGNED (ORIGINAL EVENT CODE: ASPN); ENTITY STATUS OF PATENT OWNER: SMALL ENTITY Free format text: PAYER NUMBER DE-ASSIGNED (ORIGINAL EVENT CODE: RMPN); ENTITY STATUS OF PATENT OWNER: SMALL ENTITY |